In the paper manufacturing industry, for instance, it is commonplace to employ a series of rotating steam-heated cylinders to raise the temperature of a paper web as it passes over these cylinders, thereby increasing the drying rate of the paper web. More particularly, steam from an external source is introduced to a space defined inside each cylinder.
Subsequent to this drying step, the paper web is typically wound onto a shaft. If the temperature of the paper web is too high when it is wound, the web may curl and physical properties such as brightness, tensile strength, and caliper may also be adversely affected. To reduce or eliminate these adverse effects, it is commonplace to cool the paper web. Conventionally, cooling can be accomplished with dual-purpose cylinders—also known as “swing dryers”—that function, alternately, to both cool and dry the paper web. While the drying function, as explained above, is performed by introducing steam into the space inside the cylinder, cooling is accomplished through the introduction of water into the cylinder to cool the paper web before it is wound on the shaft.
Whereas steam naturally occupies the entire space inside the cylinder, thus ensuring the even heating of the cylinder in a drying mode, cooling water must be purposefully distributed evenly to avoid wide temperature deviations across the surface of the cylinder. Otherwise, the cylinder performs its cooling function less effectively. Conventionally, cooling water may be introduced inside the cylinder via a rotating distribution member attached to the inside of the cylinder, the member having a series of evenly-spaced holes through which the water is sprayed. Alternative means include a stationary distribution member which includes one or more fixed-position water spray-nozzles.
One such conventional swing-dryer is shown in FIG. 1 to comprise a rotatable cylinder 1 having journalled ends 2a, 2b with a rotary joint 5a or 5b, respectively, connected to each. Each journal 2a, 2b is hollow, as shown, defining an internal axial passageway communicating with the space 3 inside the cylinder.
The first rotary joint 5a forms part of a flow path through which steam S from an external source (not shown) is selectively supplied to the interior space 3. This steam flow path is also defined in part by the passageway through the journal 2a. A first rotating siphon 10 extending through the journal 2a from the interior space 3 to the rotary joint 5a defines a flow path for evacuating steam condensate from the interior space 3 and discharging it to an outlet OS connected to the rotary joint 5a. 
The second rotary joint 5b forms part of a flow path through which air A and cooling water W are selectively supplied to the interior space 3, the water being distributed within that space through nozzles defined in a support spider 12. A second rotating siphon 11 extending through the journal 2b from the interior space 3 to the rotary joint 5b defines a flow path for evacuating cooling water from the interior space 3 and discharging it to an outlet OW connected to the rotary joint 5b. 
While prior art swing dryers satisfactorily perform their heating and cooling functions, they are attended by certain drawbacks. For instance, the presence of multiple, mechanically complex rotary joints, such as shown in the exemplary swing-dryer of FIG. 1, necessarily increases maintenance costs and complexity. Also, water distribution within existing swing dryers can be uneven, leading to unwanted variations in temperature across the cylinder. Further, evacuation of steam condensate and, alternately, cooling water requires high pressure differentials within rotating siphons. Still further, the flow of steam, air, and water, as well as the distribution cooling water cannot be independently controlled. It would thus be desirable to provide a dual-purpose cooling/drying cylinder which is simpler and less expensive to maintain, and which more efficiently serves the heating and cooling functions.